Method of making cigarette filter rods



y 1967 J. B. ARTHUR ET AL 3,329,543

METHOD OF MAKING CIGARETTE FILTER RODS Filed March 8, 1963 u Q w W INVENTORS JAMES B. ARTHUR JOSEPH R. GODW/N RICHARD E SZ'PIERRE United States Patent 3,329,543 METHOD OF MAKING CIGARETTE FILTER RODS James B. Arthur, Joseph R. Godwin, and Richard E. St.

Pierre, Charlotte, N.C., assignors to Celancse Corporation, a corporation of Delaware Filed Mar. 8, 1963, Ser. No. 263,855 2 Claims. (Cl. 156152) The present invention relates to a novel process and apparatus for opening tow.

A tow is a bundle of substantially endless or continuous filaments having little or no twist holding the filaments together. While there is no precise lower limit to the denier or weight per unit length of a tow, as contrasted with a zero-twist continuous multifilament yarn, for the purposes of this application the term tow will have reference to a bundle made up of a relatively large number of filaments, advantageously several hundred and preferably several thousand filaments.

Tows find application in the production of staple fibers by cutting, in the production of cigarette filters, in the production of non-Wovens, and the like. For many of these uses it isdesirable that the product have as much bulk as possible. Such bulk can be imparted to the tow by a variety of methods including, most preferably, a crimping operation. Crimping may be effected by passage between the teeth of a pair of gears, by false twisting, by passage through a stuffing box crimper, or the like, possibly using steam or hot air to help set the crimp. These crimping techniques operate on the whole bundle of filaments so that each filament is crimped along with its neighbors, the crimps of adjacent filaments being in registry. For example, a cellulose acetate tow of 10,000 filaments crimped to about 5 crimps per inch in a stufiing box has the appearance of a flat ribbon about 1 inch wide and accordion pleated across the width. Adjacent filaments cling lightly to one another so that the registry is not easily undone even by moderate manipulation.

One technique which has been proposed for deregistering the crimps of adjacent filaments in a crimped tow involves applying a large tension thereto, of the order of magnitude of 0.2 or more grams per denier, by pulling the tow along while braking its advance; the filaments thereby are temporarily straightened out, upon release snapping back and blooming out with the filaments deregistered. While this product is suitable for some purposes, the crimp is necessarily partially lost, e.g. a length of tow which in crimped condition runs a linear inch may be straightened out to two inches in length 100% crimp), only to be one and a half inches (50% crimp) after deregistration. Ideally the length after deregistration should be an inch, just as before, deregistration achieving bulking without loss of crimp.

A technique which has largely supplanted tension deregistration involves passage of the crimped tow between a pair of cooperating surfaces at least one of which is not smooth. Preferably at least two pairs of cooperating surfaces, e.g. rolls, are provided with the tow running horizontally therebetween.

It is an object of the present invention to provide a novel process and apparatus for deregistration of the crimps of the adjacent filament of a crimped tow.

It is a further object of the invention to provide a process and apparatus for opening or deregistering a crimped tow which produces an opened tow only slightly longer than the tow before opening.

Another object of the invention is to provide a process and apparatus permitting moderate latitude, at the will of the operator, in the ratio of the length of the opened tow to the length of the tow before opening.

Other objects and advantages of the invention will become apparent from the following detailed description and claims, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of an apparatus for producing cigarette filter plugs from a bale of tow.

In accordance with one aspect of the present invention there are provided at least two pairs of vertically offset cooperating surfaces. Advantageously the surfaces are rolls adapted to rotate either by a positive drive or idly by contact with a rotating roll. Advantageously one roll of each set is rigid while the other has a yielding surface, e.g. steel versus rubber or synthetic elastomer, and the rolls are urged into contact so that both rotate upon driving of but one. At least one roll of one set is not smooth surfaced so that all filaments across the width of a tow passed therebetween will not be identically treated.

In one embodiment, there are provided two pairs of rolls with their nips in vertical alignment. One roll of each pair is driven and has a smooth rubber surface. The other surface of each pair is idly mounted and spring urged into contact with its driven mate to be caused to rotate thereby. The idle roll has a helical thread cut in its steel surface. Advantageously the lower driven roll is driven at a surface speed faster than that of the upper driven roll, the tow passing downwardly. Thereby the tow is subjected, while being fed along a predetermined path, to a differential gripping action between a plurality of points spaced from one another both longitudinally and transversely of the path, so that certain laterally spaced sections of the tow are positively gripped relative to other laterally spaced sections of the tow, alternating with the said gripped sections, which are not gripped at all or are gripped at different relative points. In this manner, there is produced, as a function of the differential positive gripping of the tow, a relative shifting of adjacent filaments longitudinally of the tow, whereby the crimps are moved out of registry with one another. Preferably, although not necessarily, the differential gripping action is such that a relative longitudinal displacement between adjacent filaments of the tow is also effected, so that the combination of two transverse filament movements brings about the complete opening of the tow.

By way of definition, the term gripping (or any variant thereof) is used herein to denote the confinement of the tow by two opposed members which tightly engage the tow at its opposite faces, and the term differential gripping is used to denote the confinement of the tow between two opposed members, as Well as between sets of such opposed members, which have zones in which the tow is tightly engaged by the members alternating with zones in which the tow is only loosely or not engaged by the said members. The terms exclude a mere one-sided frictional sliding engagement between the tow and a member past which the tow moves.

The non-smooth surface has been described as preferably helical, this being one of the easiest surfaces to produce and one of the most satisfactory to work with. Advantageously there are about to threads per inch and the ridges which contact the smooth surface are flattened. Each grooved roll may be helically grooved in opposite directions from its center to its ends, or may be continuously helically grooved in either direction across the roll. Where several helical rolls contact the tow in sequence, the arrangement of grooves can be alike on successive rolls or in opposite directions on successive rolls or grooved from the center to the ends in opposite directions on successive rolls.

While helical threads are preferred the surfaces of the non-smooth rolls may be formed of circular or cylindrical ridges or of elliptical or undulating rings. It can even comprise a checkerboard of alternated raised and lowered surfaces, or it can comprise spaced projections for pinching the tow against the cooperating surface.

When use to open a crimped tow intended for use in making cigarette filters it has been found useful to employ two sets of rolls whose hips are about 10 to 50 inches and preferably about 15 to inches apart. While the tow path in moving between roll sets may be inclined as much as 45 to the vertical, advantageously its inclination is less than about 25 and preferably it is substantially vertical. The profiled or non-smooth roll of each pair is advantageously urged against the smooth roll with a force of about 5 to or more and preferably about 5 to 15 pounds per linear inch of contact between the rolls. Lower forces may result in excessive slippage where the tow is not extremely heavy, and higher forces may result in injury to the roll surfaces and to tow passing therebetween.

The first or rear driven roll pulls the tow along from a bale or ball warp over bars which straighten it out slightly and control the sidewise motion. The surface speed of the rear driven roll generally ranges from about 50 to 110% of the speed at which the opened tow is ultimately received by the garniture and fed to the belt of a cigarette wrapping machine by which it is formed into filter tips; preferably the speed is about 75 to 100% of the belt speed, i.e. the tow in the filter tips is substantially as long as in the crimped unopened state. The front, second or downstream driven roll operates at a speed varying from about 120 to 300% and preferably from about 150 to 225% of the upstream driven roll, the exact value for maximum openness varying from tow product to two product.

The novel apparatus permits a relatively wide latitude in the characteristics of filters which may be produced from any one particular tow item, a wider latitude than is possible by any other apparatus. For example, if a tow of 10,000 filaments of 7 denier each is passed between two pairs of rolls operating at that speed ratio which gives maximum opening using a cigaretting machine operating at predetermined fixed speed, it will be possible to produce useful filter tips over a wide range of rear roll speeds. Surprisingly this is not possible to the same extent if the tow path between roll pairs is horizontal. As a consequence, a filter manufacturer can stock a single tow item and nonetheless produce filters exhibiting a whole spectrum of weights, pressure drops and smoke removal elficiencies.

The opened tow when used for making cigarette filters may pass through an air spreader and plasticizer applicator on its way to the cigarette machine garniture; alternatively, because of its high bulk the opened tow may be fed directly to the garniture and will make satisfactory filters even without plasticizing and subsequent curing to effect bonding.

The tow is preferably composed of a plurality of crimped continuous filaments of an organic derivative of cellulose, e.g. esters or ethers of cellulose such as cellu-.

lose acetate, cellulose propionate and cellulose acetate propionate, highly esterified cellulose containing less than 0.29 free hydroxyl groups per anhydroglucose unit such as cellulose triacetate, and the like. Other filamentary materials such as rayon (regenerated cellulose), lineary superpolyamides such as nylon-6 and nylon-66, linear polyesters, and polymers and copolymers of vinylidene compounds such as ethylene, propylene, vinylidene cyanide, acrylonitrile, and the like, can also be employed. The number of filaments and the total denier can vary within widelimits, but in preparing filters for conventional cigarettes which are approximately 24 to 26 mm. in circumference, the number of filaments generally varies between about 5,000 and 33,000, and the total denier ranges from about 35,000 to 160,000, computed or uncrimped tow. The number of crimps per inch in the tow can range up to about 3040, but preferably averages between about 4 and 25, e.g. 8 to 12 computed on an inch of straightened tow. The percent crimp, i.e.

tensioned length-contracted length contracted length ranges from about 50 to 200% and preferably from about 75 to 150%. The deregistration of the crimps of adjacent filaments prevents channeling and permits production of a firm filter even with a tow of a smaller total denier than normally utilized. In addition, the filtering efiiciency increases so that a given efficiency can be achieved using less tow and thus with less resistance to draw, i.e. at a lower pressure drop.

If a plasticizer is used, its identity will, of course, depend on the composition of the tow. With cellulose acetate, such compositions as triethyl citrate, dimethoxy ethyl phthalate and methyl phthalyl ethyl glycolate may be employed, but glycerol triacetate (triacetin) is preferred. The proportion of plasticizer applied generally varies from about 2% to 30% by weight of the tow to which it is applied, and preferably from about 4% to about 15%.

A vertical tow path permits plasticizer to be applied to both faces of the tow uniformly. By contrast, if the tow moves horizontally plasticizer sprayed at the top will affect the tow differently from plasticizer sprayed at the bottom, due to gravity. Moreover, if a spray device is positioned above the tow there is raised the possibility of dripping of plasticizer with resultant non-uniformities in feel and performance.

Referring now more particularly to the drawing, in FIG. 1 there is shown a bale of tow 11 from which a crimped tow 12 is drawn upwardly over a bar 13, passing horizontally through an air spreader 14 and then about direction changing tension bars 15, 16 and 17. These serve to flatten the tow band, to widen it, to remove fold overs and to pre-tension the tow prior to opening. Bar 17 is positioned to drop the tow 12 substantially vertically into the nip formed between driven smooth rubber roll 19 and helically grooved idle steel roll 18 urged by a spring (not shown) against roll 19. The tow 12 next passes between steel roll 20 and rubber roll 21, constructed and arranged similarly to rolls 18 and 19 except that roll 21 is driven almost twice as fast as roll 19. The now opened tow 12 passes to a collector specifically the garniture trumpet 22 of a cigarette making machine 24 wherein the tow is wrapped in paper to form a continuous rod 25 which is severed by a knife 26 into filter plugs 27 of predetermined length.

The garniture trumpet is vertically offset relative to the nip of rolls 20, 21 in order to eliminate any direction changing devices between rolls and trumpet. The vertical distance advantageously does not exceed 20 inches since a longer length of unsupported tow will, by its own weight, pull out some crimp from the opened tow which at this point is prone to crimp loss (possibly because of the absence of support from adjacent filaments such as occurs in the unopened tow). On the other hand the trumpet should not be too close to the nip, e.g. less than about 6 inches since occasionally the tow may tend to pile up on the trumpet and this may back up to the rolls with jamming of the apparatus and non-uniformities in the rods. Advantageously the trumpet is from about 8 to 16 inches below the roll nip.

Advantageously the garniture trumpet is also offset horizontally relative to the nip of rolls 20, 21 which nip preferably lies in a horizontal plane also containing the axes of rolls 20, 21. By offsetting the trumpet at least 3 inches horizontally, the aforementioned pile up of tow on the trumpet is avoided, any temporary excesses resulting in a small catenary bend between the nip and trumpet. Preferably the horizontal offset is at most about 6 inches. The horizontal offset, however, desirably does not exceed about 12 inches since too large a horizontal span will result in crimp loss due to its own weight as well as due to the force needed to advance the tow. Moreover, too large a horizontal offset will cause the opened tow to lap around one of the rolls to some extent which will necessitate some pulling, i.e. tension, to advance the tow to the trumpet with resulting crimp loss; if guide pins are utilized to prevent such lapping they too will increase the tension on the tow.

Thus, one feature of the invention involves positioning of the garniture trumpet within about 12 inches of the roll nip but below and horizontally offset relative thereto so that the tow falls by gravity into the trumpet without being pulled into the trumpet or lapping the rolls, i.e. without any tension applied to the opened tow. The spacing must be sufficiently close to prevent the weight of the unsupported length of opened tow from introducing such tension which would result in crimp loss and thereby reduce the maximum apparent denier of filter rods producible from any particular tow item.

Not to be minimized is the fact that the vertical arrangement of the tow opening rolls permits the tow bale to be positioned directly adjacent the filter rod wrapping machine with attendant saving in floor space. This is especially important when installing opening equipment in plants where the rod wrapping machines are in fixed positions so that there is but limited spaced therebetween for installation or positioning of further equipment or tow bales.

The invention will now be further described in the following illustrative examples.

Example I A tow comprising 10,000 secondary cellulose acetate filaments of 7 denier each and having 12 crimps per inch and 100% crimp, is threaded through the apparatus of FIG. 1. The bar 17 is positioned 1 foot above the nip of rolls 18, 19 which in turn is 20 inches above nip of rolls 20, 21, the latter being inches above garniture 22. Rolls 19 and 21 are made of rubber, 6% inches in diameter. Rolls 18 and 20 are of the same external diameter but are made of steel having cut therein a helical thread of 14 turns per inch. Each turn has a 60 apex angle at its base and a fiat 0.017 inch wide. Rolls 18 and 20 are urged against rolls 19 and 21 with a spring force of 10 pounds per linear inch of contact.

The ratio of the surface speed of roll 21 to that of roll 19 is adjusted until maximum opening is achieved, in this case at 1.7:1; this is visually determined and may vary slightly from one tow item to another. With this ratio now held constant, the speed of roll 19 (and thus of roll 21) is adjusted relative to the speed of the cigarette making machine which wraps the tow into a rod. Below a certain speed of roll 19 there is so little tow in the rod that it dimples and wrinkles. This minimum speed in this instance is 78% of the speed at which the rod is produced and corresponds to a minimum tow weight per unit length. This in turn can be expressed as an .apparent denier (or weight in grams of 9000 meters of rods excluding paper and glue) in contrast with the nominal denier of 70,000. In this example the minimum apparent denier is 79,500. The speed can be increased relative to the rod making speed until appreciable slack is developed between rolls 20, 21 and garniture 22 at which speed wrapping becomes erratic and rod weight becomes non-uniform. This maximum speed in this run is 88% of the rod making speed corresponding to an apparent denier of 91,200. Thus good filter rods can be produced at apparent deniers between 79,500 and 91,200 or over a range of By contrast, if opening is effected using a system having a horizontal tow path (in accordance with the disclosure of application Ser. No. 151,900 now US. Patent 3,156,- 016 but without plasticizing or air spreading following the grooved rolls), the minimum apparent denier of such control rods is 80,000 and the maximum 85,400, both values being less than for the vertical path. The spread of 5400 denier is only 6.8% of 80,000 denier, less than half the 14.7% spread with the vertical system. Consequently with this single tow item of 7/ 70,000 a plug manufacturer can produce rods having a Wide range of weights and hence a wide range of pressure drops and smoke removal efficiencies. By contrast, where the spread is narrow, if a rod weight is desired outside the narrow range it becomes necessary to stock another tow item.

All the filter rod manufacturer need do is determine the optimum ratio of surface speed of roll 21 to roll 19 for the particular tow item and then lock this ratio onto the drives. Then to produce any particular rod item within the range of possibilities the machine operator need only change a single control, viz. the speed of driven roll 19. Roll 21 will automatically speed up and the rod maker will operate at constant speed.

It has surprisingly been found that for a given rod Weight rods produced in accordance with the present invention have a somewhat higher pressure drop and smoke removal efliciency than rods produced from the control system, i.e. with the present invention a given smoke removal efficiency can be achieved at a lower rod weight.

Example 11 The foregoing process was repeated with a variety of secondary cellulose acetate tow items, as indicated in the following table, the vertical tow path consistently giving a wide spread for weight of rods producible from a given tow.

TABLE Apparent Denier TOW Item Spread, Percent Min. Max.

It is to be understood that the foregoing detailed description is merely given by Way of illustration and that many variations may be made therein without departing from the spirit of the invention.

Having described the invention, what is desired to secure by Letters Patent is:

1. The process for making cigarette filter rods from a tow made up of about 5,000 to 33,000 continuous filaments, having a nominal total denier of about 35,000 to 160,000, about 4 to 40 crimps per inch and about 50 to 200% crimp, which comprises removing said tow from a package, pretensioning said tow, passing said tow substantially vertically downwardly between at least two pairs of rolls positioned about 10 to 50 inches apart vertically, at least one roll of one of the pairs being grooved, at least one roll of each pair being driven with the lower driven roll having a peripheral speed about to 300% that of the upper driven roll, each pair of rolls having a substan- 7 8 tially horizontal nip, directly receiving said tow from the 2. Process as in claim 1 in which the lower pair of said lower nip on a collector positioned about 6 to 20 inches P of 10115 compnses at least 0116 grooved I011- vertically below and oifset laterally about 3 to 12 inches relative to said nip, and forming said tow into cigarette References Cited filter rods, the peripheral speed of said first driven roll 5 UNITED STATES PATENTS ranging from about 50 to 110% that at which said tow is 2638634 5/1953 Hare 19-66 X formed into rods said process making for a wider latitude 2908045 10/1959 SteYenS 19*66 3,016,581 1/1962 Smith 19- 65 1n the characteristics of the filter rods produced from a 3,156,016 11/1964 Dunlap et a1 given tow, as compared to the latitude obtained when said 10 pairs are so arranged that the tow passes horizontally be- EARL BERGERT, Primary Examiner tween said nips. P. DIER, Assistant Examiner. 

1. THE PROCESS FOR MAKING CIGARETTE FILTER RODS FROM A TOW MADE UP OF ABOUT 5,000 TO 33,000 CONTINUOUS FILAMENTS, HAVING A NOMINAL TOTAL DENIER OF ABOUT 35,000 TO 160,000, ABOUT 4 TO 40 CRIMPS PER INCH AND ABOUT 50 TO 200% CRIMP, WHICH COMPRISES REMOVING SAID TOW FROM A PACKAGE, PRETENSIONING SAID TOW, PASSING SAID TOW SUBSTANTIALLY VERTICALLY DOWNWARDLY BETWEEN AT LEAST TWO PAIRS OF ROLLS POSITIONED ABOUT 10 TO 50 INCHES APART VERTICALLY, AT LEAST ONE ROLL OF ONE OF THE PAIRS BEING GROOVED, AT LEAST ONE ROLL OF EACH PAIR BEING DRIVEN WITH THE LOWER DRIVEN ROLL HAVING A PERIPHERAL SPEED ABOUT 120 TO 300% THAT OF THE UPPER DRIVEN ROLL, EACH PAIR OF ROLLS HAVING A SUBSTANTIALLY HORIZONTAL NIP, DIRECTLY RECEIVING SAID TOW FROM THE LOWER NIP ON A COLLECTOR POSITIONED ABOUT 6 TO 20 INCHES VERTICALLY BELOW AND OFFSET LATERALLY ABOUT 3 TO 12 INCHES RELATIVE TO SAID NIP, AND FORMING SAID TOW INTO CIGARETTE FILTER RODS, THE PERIPHERAL SPEED OF SAID FIRST DRIVEN ROLL RANGING FROM ABOUT 50 TO 110% THAT AT WHICH SAID TOW IS FORMED INTO RODS SAID PROCESS MAKING FOR A WIDER LATITUDE IN THE CHARACTERISTICS OF THE FILTER RODS PRODUCED FROM A GIVEN TOW, AS COMPARED TO THE LATITUDE OBTAINED WHEN SAID PAIRS ARE SO ARRANGED THAT THE TOW PASSES HORIZONTALLY BETWEEN SAID NIPS. 